Self adhesive labels, films, and tapes have become very popular for their versatility and ease of use, since no extra glue is required to make them adhere to a substrate. They are used extensively in offices and by school children of course, but also large volumes are used by industries for labelling their products. The self-adhesive labels are provided attached to a release liner made of paper or a polymeric carrier and usually coated at least on one side with a release agent, most often consisting of a silicone release layer, which provides a release effect against the adhesive of the label. Other release agents are sometimes used, such as wax, paraffin, low surface energy fluorinated compounds, etc. Examples of silicone coated liners are given in U.S. Pat. No. 5,275,855, JP07279099, and U.S. Pat. No. 6,036,234. Silicone or other release agent coated liners are also used more generally as backing in the production of films, such as PVC films. The total global consumption of release liners in 2008 is believed to be around 32 Billion square meter of coated product, which is equal to 75% of the surface area of Switzerland. Approximately 85% of this material is paper based and 15% is plastic based (cf. http://en.wikipedia.org/wiki/Release_liner).
After use of the labels, films or tapes supported on said carriers, the liners are pure waste and must be disposed of. Considering the volumes mentioned above, this results in a great source of waste, which is coming under the scrutiny of several governments which intend to tax the disposal thereof as packaging material. The issue is rendered even more sensitive for cellulose release liners because the cellulose carriers are usually made of virgin material which has never gone through any recycling cycle yet. Recycling paper coated with a release agent by conventional repulping methods for making printing or packaging paper is possible but difficult without loss in quality because of insufficient disintegration of the fibres and sticking of resin particles on the rolls and felts due to the release coating. Solutions to recycle silicone coated paper were proposed in U.S. Pat. No. 5,567,272 and EP587000, requiring the use of salts of phosphoric esters of fluorinated alkanols to chemically separate the silicone release agent from the cellulose sheet carrier, the latter being forwarded to a recycled paper manufacturing line. Alternatively, DE4302678 and U.S. Pat. No. 5,573,636 propose a specific release coating comprising a solid material, preferably in the form of microcapsules, which swell in contact with water and promote separation of the coating from the pulp in an aqueous medium, for repulping the cellulose fibres.
The building and transportation industries are making more and more use of cellulosic materials coming from old newspaper, cardboard, etc. to manufacture heat and acoustic insulating materials in the form of loose fibrous materials, fibrous mats with or without skins, panels of varying stiffness, and even hollow blocks; the manufacture of blocks and panels may require the use of a binder, a glue or a cement. Cellulose insulating material has a much lower “embodied energy” than e.g., glasswool or rockwool insulation, wherein the embodied energy is the sum of the energy to transport the raw material to the manufacturing facility+the energy for manufacturing the product+the energy to deliver the manufactured product. General information concerning cellulose insulating materials can be found e.g., in: http://www.ownerbuilderonline.com/blown-cellulose-insulation.html, http://www.cellulose.org/CIMA/GreenestOftheGreen.php; http://www.youtube.com/watch?v=bwcblg6g5Cs&feature=related.
DE19653243 discloses a heat and acoustic insulating material made of cellulose fibres from old paper and impregnated with e.g. boric acid or salts thereof as flame retardant and against formation of mould, wherein the cellulose fibres come at least partly from wet glue applied paper labels.
DE4334200 discloses a process for producing thermally insulating materials from waste paper by means of a mild hydromechanical treatment with subsequent drying using hot air. The boards or mats formed therefrom have a very low specific density, from which a high thermal insulation value results.
WO2002090682 discloses sound insulation partitions comprising at least a substantially homogeneous self-supporting rectangular cellulose mat having a density ranging between 200 and 800 kg/m3, said mat essentially consisting of fibres derived from the treatment of practically lignin-free recycled papers or paperboards, the bond between the fibres within the mat being obtained at least partly during the production of the mat by wet process.
DE4402244 discloses a sound and heat insulating material made from a dried, aqueous suspension containing 10-50 wt % chopped waste paper and 90-10 wt % animal and/or plant fibres such as hairs, short wool fibres, etc. The mixed suspension is placed on a sheet former, in particular on a sieve, where the water is removed. A flat flexible mat is formed and subsequently dried and finished.
DE19835090 discloses a method of production of cellulose insulation materials including the control of various parameters in the mill to obtain a homogeneous material comprising additives.
DE3641464 discloses an insulating board made of a mixture of old newspapers free fom any surface treatment or fillers, natural fibres, and a glue and/or reaction promoter. EP0617177 discloses a skin/core building element for heat insulation and vibration damping wherein the core is made of a filler of paper like material and thin thermoplastic component to act as binder upon melting.
DE4403588 discloses heat insulation components constructed in the form of hollow blocks and prefabricated wall boards, produced, in particular, from pulped, water-resistant old paper, such as old labels, stickers, high-gloss paper, advertising posters and billboards (signs), mixed with water, cement and sand. In particular, a preferred mixture ranges from 50 vol % to 80 vol % of water-resistant old paper, from 10 vol % to 20 vol % of cement, and from 10 vol % to 60 vol % of sand.
US2009/0173464 discloses an acoustic panel comprising from 10-40 wt % cellulosic fibres, 0-30 wt % gypsum, 0-15 wt % starch and other components. Similarly, DE10336569 discloses a fire-resistant gypsum fibreboard made from a mixture of 87-78% gypsum and 13-22% cellulose fibres made from used paper as a reinforcing component and a 35-50% boric acid based on the fibre weight for raising the flame resistance.
In the transportation industry, DE20200550114581 discloses a cellulose based insulation material for the exhaust system of a combustion engine and US2002025421 discloses a sound absorbing insulation material containing cellulose for the cabin of a motor vehicle. DE4331567 discloses a light weight fire protection element for the aircraft industry made of waste paper mixed with a special binder, resulting in an “apparently paradoxical fireproof material made of paper”.
There remains in the art a need for finding routes to recycle release coated carriers of the type used as liners for labels. In parallel, there remains a lot to do in the fields of recycled paper and of insulation materials for the building, transportation, and other industries to provide an insulation material which is cheap, and has good thermal and acoustic insulation and damping properties. The present invention proposes a solution to these and other problems in the art of recycling.